The invention relates to an internal combustion engine having eight cylinders in a V-configuration wherein a first, a second, a third and a fourth cylinder, arranged side-by-side in series, form a first cylinder bank; and a fifth, a sixth, a seventh and an eighth cylinder, arranged side-by-side in series, form a second cylinder bank, which lies opposite the first cylinder bank.
German Published Patent Application DE 199 54 689 A1 discloses a generic internal combustion engine having eight cylinders in a V-configuration. A first, a second, a third and a fourth cylinder arranged side-by-side in series form a first cylinder bank; and a fifth, a sixth, a seventh and an eighth cylinder also arranged side-by-side in series form a second cylinder bank opposite the first cylinder bank. Furthermore, the internal combustion engine has a crankshaft with a 90° bend, that is, a cross-plane crankshaft, and an ignition interval of 90° crank angle (90° CA) from cylinder to cylinder. For the charge cycle each cylinder bank has an intake camshaft and an exhaust camshaft in order to actuate the intake gas exchange valves and the exhaust gas exchange valves for each cylinder. In order to improve, inter alia, the smooth running of the internal combustion engine, in particular in neutral and under smaller partial loads, it is proposed to provide means for implementing differing exhaust valve lift progressions of at least two cylinders arranged in one cylinder row in order to reduce the overlapping opening phases of these exhaust gas exchange valves. In this context the intake valve and the exhaust valve of one of the two cylinders are themselves in an overlapping opening phase.
Even if this prior art internal combustion engine with eight cylinders in V-configuration does not have, in principle, any drawbacks, the object of the present invention is to provide an additional measure to reduce the rough running of the internal combustion engine, in particular, in neutral and in the lower partial load range.
This and other objects are achieved by an internal combustion engine with eight cylinders in V-configuration, wherein a first, a second, a third and a fourth cylinder, arranged side-by-side in series, form a first cylinder bank; and a fifth, a sixth, a seventh and an eighth cylinder, arranged side-by-side in series, form a second cylinder bank, which lies opposite the first cylinder bank. The internal combustion engine has a cross-plane crankshaft and an ignition interval of 90° crank angle from cylinder to cylinder. Each cylinder bank has an intake camshaft and an exhaust camshaft in order to actuate at least one intake gas exchange valve and one exhaust gas exchange valve for each cylinder. The intake gas exchange valves of the cylinders, which form each cylinder bank and are actuated according to a 90° crank angle in the same cylinder bank, have a larger valve lift than the intake gas exchange valves in the same cylinder bank actuated immediately prior thereto. The intake gas exchange valves in the same cylinder bant actuated immediately prior thereto have a smaller valve lift than all of the remaining intake gas exchange valves of both cylinder banks.
This further development according to the invention makes it possible to attain in an advantageous way an equalization of the specific work of the individual cylinders in each cylinder bank and, thus, to reduce the rotational irregularity in the critical operating ranges, in particular in neutral and in the lower partial load range. Owing to this inventive measure the use of applied measures can be avoided, a state that leads to an improvement in the efficiency (less fuel consumption and/or CO2 emission), the smooth running and raw pollution emission. In addition, the improved smooth running makes it possible to lower the idling speed and, as a result, leads to a reduction in the idling fuel consumption.
In a first preferred exemplary embodiment, the intake gas exchange valves are actuated via one intermediate element each. The larger valve lift occurs by way of a lift correction of the intermediate element. The intermediate element may be, for example, a drag or rocking lever.
In a second preferred exemplary embodiment, the intermediate element is supported at the cylinder head on a play compensating element. The larger valve lift occurs by way of a height and/or angular position correction of the play compensating element. The play compensating element may be, for example, a hydraulic play compensating element.
In a third preferred exemplary embodiment, the intake gas exchange valves are actuated by way of a variable lift valve timing mechanism with a lift adjustment element. The larger valve lift occurs by way of a lift correction of the lift adjustment element.
Particularly preferably, the larger and/or the smaller lift height ranges from 0.005 mm to 1.0 mm with respect to the remaining intake gas exchange valves. This preferred range of values particularly achieves the inventive effect.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.